Detonator output interrupter for downhole tools

ABSTRACT

An apparatus for selectively activating a downhole tool by using a shockwave generated by a detonator assembly may include an outer housing having a bore and an inner housing disposed in the bore of the outer housing. The inner housing may include a chamber having at least one canted surface, an inlet communicating with the chamber and being positioned between the chamber and the detonator assembly, an outlet communicating with the chamber and being positioned between the chamber and the downhole tool, and an energy blocker disposed in the chamber and being freely movable in the chamber as the inner housing changes orientation relative to a vertical datum. The energy blocker axially aligns with the inlet and the outlet when the inner housing is angularly offset less than a specified amount relative to a vertical datum.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Application Ser.No. 61/977,441, filed Apr. 9, 2014, the entire disclosure of which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to devices and methods for firing one ormore downhole tools. More particularly, the present disclosure is in thefield of control devices and methods for enhancing the reliability offiring systems used to fire a ballistic downhole tool.

BACKGROUND

One of the activities associated with the completion of an oil or gaswell is the perforation of a well casing. During this procedure,perforations, such as passages or holes, are formed in the casing of thewell to enable fluid communication between the wellbore and thehydrocarbon producing formation that is intersected by the well. Theseperforations are usually made with a perforating gun loaded with shapedcharges. The gun is lowered into the wellbore on electric wireline,slickline or coiled tubing, or other means until it is at a desiredtarget depth; e.g., adjacent to a hydrocarbon producing formation.Thereafter, a surface signal actuates a firing head associated with theperforating gun, which then detonates the shaped charges. Projectiles orjets formed by the explosion of the shaped charges penetrate the casingto thereby allow formation fluids to flow from the formation through theperforations and into the production string for flowing to the surface.

Many oil well tools incorporate a high-order detonation as part of theiroperation. When these tools are fired prematurely, it can be costly andtime consuming to repair the well and re-attempt the desired wellboreoperation. The present disclosure relates to methods and devices forpreventing premature high-order detonations from initiating operation ofoil well tools.

SUMMARY

In aspects, the present disclosure provides an apparatus for selectivelyactivating a downhole tool by using a shockwave generated by a detonatorassembly. The apparatus may include an outer housing having a bore andan inner housing disposed in the bore of the outer housing. The innerhousing may include a chamber having at least one canted surface, aninlet communicating with the chamber and being positioned between thechamber and the detonator assembly, an outlet communicating with thechamber and being positioned between the chamber and the downhole tool,and an energy blocker disposed in the chamber and being freely movablein the chamber as the inner housing changes orientation relative to avertical datum. The energy blocker axially aligns with the inlet and theoutlet when the inner housing is angularly offset less than a specifiedamount relative to a vertical datum.

In aspects, the present disclosure provides a method for selectivelyactivating a downhole tool by using a shockwave generated by a detonatorassembly. The method employs detonator output interrupters according tothe present disclosure along with one or more well tools that areconveyed to a target depth across a wellbore that has vertical anddeviated sections.

It should be understood that examples of the more important features ofthe disclosure have been summarized rather broadly in order that thedetailed description thereof that follows may be better understood, andin order that the contributions to the art may be appreciated. Thereare, of course, additional features of the disclosure that will bedescribed hereinafter and which will in some cases form the subject ofthe claims appended thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

For detailed understanding of the present disclosure, references shouldbe made to the following detailed description of the preferredembodiment, taken in conjunction with the accompanying drawings, inwhich like elements have been given like numerals and wherein:

FIG. 1 schematically illustrates an elevation view of a surface facilityadapted to perform one or more pre-defined tasks in a wellbore using oneor more downhole tools;

FIG. 2 illustrates a side sectional view of a detonator outputinterrupter according to one embodiment of the present disclosure;

FIG. 3 illustrates a side sectional view of the FIG. 2 detonator outputinterrupter in a horizontal orientation; and

FIG. 4 illustrates a side sectional view of the FIG. 2 detonator outputinterrupter in an inverted orientation.

DETAILED DESCRIPTION

The present disclosure relates to devices and methods for providing adetonator output interrupter to selectively initiate operation of one ormore downhole tools. The present disclosure is susceptible toembodiments of different forms. There are shown in the drawings, andherein will be described in detail, specific embodiments of the presentdisclosure with the understanding that the present disclosure is to beconsidered an exemplification of the principles of the disclosure, andis not intended to limit the disclosure to that illustrated anddescribed herein.

Referring to FIG. 1, there is shown a well construction and/orhydrocarbon recovery facility 10 positioned over a subterraneanformation of interest 12. The facility 10 can include known equipmentand structures such as a rig 16, a wellhead 18, and cased or uncasedpipe/tubing 20. A work string 22 is suspended within the wellbore 14from the rig 16. The work string 22 can include drill pipe, coiledtubing, wire line, slick line, or any other known conveyance means. Thework string 22 can include telemetry lines or other signal/powertransmission mediums that establish one-way or two-way telemetriccommunication. A telemetry system may have a surface controller (e.g., apower source) 24 adapted to transmit electrical signals via a cable orsignal transmission line 26 disposed in the work string 22. To performone or more tasks in the wellbore 14, the work string 22 may include adownhole tool 50 that is activated by a high-order detonation.

Conventionally, the downhole tool 50 is conveyed by the work string 22along the various sections of the wellbore 14 until a desired targetdepth is reached. The wellbore 14 may have a complex geometry thatincludes one or more vertical sections 30 and one or more deviatedsections 32. While shown as perfectly vertical and perfectly horizontal,the vertical sections 30 and the deviated sections 32 may vary in actualangular offset from a vertical datum. In some instances, the targetdepth is in the deviated section 32 of the wellbore 14. As discussedbelow, detonator output interrupters according to the present disclosurecan prevent premature activation while the downhole tool 50 is beingconveyed to the target depth.

Referring to FIG. 2, there is sectionally illustrated one non-limitingembodiment of a detonator output interrupter 100 made in accordance withthe present disclosure. The detonator output interrupter 100 canselectively prevent an energetic discharge, such as a shockwave,generated by the detonator assembly 110 from energetically activating adownhole tool 120. The detonator assembly 110 may include a firing head112 and an initiator 114. The downhole tool 50 can be a perforating gunor any other device that uses a high-order detonation and associatedshock wave to initiate operation. As shown, the downhole tool 50 may befired by detonating a bi-directional booster charge 122 that ignites adetonating cord 124.

In one embodiment, the detonator output interrupter 100 may include anouter housing 130, an inner housing 132, and an energy blocker 134.

The outer housing 130 may be formed as a cylindrical structure that actsas a bulkhead and an enclosure for the internal components of thedetonator assembly 110 and the detonator output interrupter 100. In oneembodiment, the outer housing has a first end 140 that connects viathreads 142 to an adjacent tool 144 and a second end 146 that connectsvia threads 148 to the downhole tool 50. The outer housing also has abore 150 in which the firing head 112, the initiator 114 and the innerhousing 132 are serially disposed. In other embodiments, thesecomponents may be disposed in separate enclosures. For example, thefiring head 112 and the initiator 114 may be positioned in a separatesub.

In one arrangement, the inner housing 132 may also be a cylindricalstructure that is configured to retain the energy blocker 134 and tochannel the shockwave generated by the detonator assembly 110 to thedownhole tool 50. The inner housing may include an inlet 152 and anoutlet 154 that communicate with a chamber 156. The inlet 152 and theoutlet 154 are axially aligned with one another and may be concentricwithin the inner housing 132 as shown or may be offset from the centralaxis of the inner housing 132.

The chamber 156 includes opposing surfaces 158 that are substantiallytransverse to the vertical datum 102 and a cylindrical inner surfacethat is substantially parallel to the vertical datum 102. Bysubstantially, it is meant within 30 degrees. The inlet 152 has one endproximate to the initiator 114 and another end terminating at a firstsurface of the opposing surfaces 158. The outlet 154 has one endproximate to the downhole tool 50 and another end terminating at asecond surface of the opposing surfaces 158. The surfaces are generallycanted such that they slope toward the inlet 152 or the outlet 154. Thatis, the surfaces 158 may be sloped to position an apex at the inlet 152or the outlet 154. For example, the surfaces 158 may have a conicalshape that positions the cone apex at the inlet 152 or the outlet 154.Generally concave shapes may also be used. The shape and amount of slopeof the surfaces 158 can control the amount of deviation needed to shiftthe energy blocker 134. The opposing surfaces 158 are shown as similarlyshaped, but they may also be dissimilarly shaped. That is, the surfaces158 may be canted the same way, canted different ways, or one may haveno cant.

The energy blocker 134 deflects, absorbs, or otherwise interrupts anenergy train generated by the detonator assembly 110 from initiating thedownhole tool 50. The energy blocker 134 is disposed in the chamber 156and can selectively obstruct the axial path along which a shockwavegenerated by the initiator 114 traveling to the booster charge 122. Theenergy blocker 134 may be formed of steel, metal, ceramics, plastics,composites, or any other material that deflects and/or breaks up theshockwave such that the energy is dissipated into the inner housing 132.In one arrangement, the detonator output interrupter 100 blocks theshock wave when the detonator output interrupter 100 is in the verticalposition (e.g., aligned with the vertical datum 102). The energy blocker134 shifts to a position that does not impede the travel of theshockwave after the tool 100 is oriented at or past a selecteddeviation. In one embodiment, the energy blocker 134 may be a sphericalbody such as a ball. In the vertical orientation shown in FIG. 2, theenergy blocker 134 gravitates to and rests over the outlet 154 becausethe surface 158 is canted.

In one non-limiting embodiment, the energy blocker 134 may be a metalball (e.g., a steel ball bearing) that is “freely movable” in thechamber 156. By “freely moveable,” it is meant that the energy blocker134 is not connected to any other structure and can freely move due togravity as the detonator output interrupter changes orientation. A ballshape allows the energy blocker 134 to roll due to gravity. However,other shapes may also be used (e.g. disk shapes). Also, actions otherthan rolling may be used (e.g., sliding, pivoting, rotating, etc.).Thus, the energy blocker 134 may use any configuration that isresponsive to gravity and can move out of contact with the inlet 152 orthe outlet 154 when the downhole tool 100 is in the appropriateorientation. The shape and weight of the energy blocker 134, as well asthe dimensions and shape of the chamber 152, can also control how muchdeviation will be needed to shift the energy blocker 134.

Referring to FIG. 3, the detonator output interrupter 100 is shown in ahorizontal orientation; i.e., the vertical datum 102 (FIG. 2) istransverse to gravity. Because of gravity, the energy blocker 134 hasfallen to a region of the chamber 156 that is radially offset from theinlet 152 and the outlet 154. Thus, a shockwave from the initiator 114travels unimpeded through the chamber 156 to the booster charge 122. Itshould be noted that a deviated orientation other than a horizontalwould also move the energy blocker 134 away in this particularembodiment.

In FIG. 4, the detonator output interrupter 100 is shown in an invertedposition; i.e., vertically flipped from the orientation shown in FIG. 2.In this vertical orientation, the energy blocker 134 gravitates to andrests over the inlet 152 because the surface 158 is canted; i.e.,sloped. However, the function of the energy blocker 134 remainsgenerally the same in that the shockwave from the initiator 114 isblocked from passing through to the booster charge 122.

One illustrative use of the detonator output interrupter 100 will bediscussed in connection with FIGS. 1-3. For clarity, the detonatoroutput interrupter 100 will be discussed with reference to perforatingguns. It should be appreciated, however, that the detonator outputinterrupter 100 is not limited to such use.

In one mode of use, the detonator output interrupter 100 is incorporatedinto the tool 50. The downhole tool 50 may be any device that isintended to be activated by using by a high-order detonation from thedetonator assembly 110. The signal for firing the detonator assembly 110may be a pressure change, an impact, a time delay, an electrical signal,or any other suitable actuating methodology. When a signal is received,the firing head 112 impacts the initiator 114. Upon impact, theinitiator 114 undergoes a high-order detonation that causes a shock waveto enter the inlet 152. Whether or not the shockwave passes successfullythrough to the booster charge 122 depends on the orientation of thedetonator output interrupter 100.

Initially, the downhole tool 50 may be conveyed along the verticalsection 30 of the wellbore 14. In this section, the orientation of thedetonator output interrupter 100 may be less than the selected minimumvalue for a deviation. Therefore, if the detonator assembly 110inadvertently generates a shock wave, then the energy blocker 134 may bein physical contact with one of the opposing surfaces 158 and axiallyaligned with the inlet 152 and the outlet 154. Thus the energy blocker134 acts as an energy barrier and/or energy absorber for thisinadvertent shock wave. Thus, the downhole tool 50 is not prematurelyinitiated.

After the downhole tool 50 has reached the target depth at the deviatedsection 32 of the wellbore, the orientation of the detonator outputinterrupter 100 may be at or greater than the selected minimum value fora deviation. The selected value for the deviation may be a 15 degree, 30degree, 45 degree, 60 degree, 75 degree, a 90 degree, or anotherintervening value. Therefore, the gravity radially shifts the energyblocker 134 out of alignment with the inlet 152 and the outlet 154.Thus, for instance, the energy blocker 134 may be radially displacedfrom the inlet 152 and the outlet 154 and resting on the opposingsurface 158 and/or the cylindrical inner surface. Now, a shockwavegenerated by the detonator assembly 110 can travel axially unimpededthrough the chamber 156, exits at the outlet 154, and ignite the boostercharge 122. The booster charge 122 detonates the detonating cord 124 orother device, which then initiates operation of the downhole tool 50.

As used above, a high-order detonation is a detonation that produceshigh amplitude pressure waves (e.g., shock waves) and thermal energy.Likewise, a high-order explosive is an explosive formulated to generatea high-order detonation when detonated. In firing head assemblies, ahigh-order detonation occurs when a firing pin percussively impacts anddetonates a detonator that includes a high-order explosive. The primaryand secondary explosive bodies, as well as the activator, may use one ormore high-explosives. Illustrative high-explosives include, but are notlimited, to RDX (Hexogen, Cyclotrimethylenetrinitramine), HMX (Octagon,Cyclotetramethylenetetranitramine), HNS, and PYX.

As used above, “selective” means that activation of the downhole toolcan occur only when the downhole tool is at a selected orientationrelative to a vertical datum 102. The selected orientation can be arange (e.g., at least thirty degrees offset from the vertical datum). Asused above, the terms “activation” and “initiation” are usedsynonymously. As used above, a shockwave is a high amplitude pressurepulse. In some conventions, an orientation less than forty five degreesfrom vertical is considered a vertical or substantially vertical and anorientation of forty five degrees or greater from vertical is considereddeviated or substantially. As used above, a vertical datum is a datumthat is substantially parallel with the direction of gravitational pull(e.g., plus or minus ten degrees).

In other embodiments, the detonator output interrupter 100 may be usedto block other energy transfer systems. For example, the detonatoroutput interrupter 100 could be used with an igniter and propellantsystem. In such an embodiment, a flame output from the igniter will beinterrupted.

The foregoing description is directed to particular embodiments of thepresent disclosure for the purpose of illustration and explanation. Itwill be apparent, however, to one skilled in the art that manymodifications and changes to the embodiment set forth above are possiblewithout departing from the scope of the disclosure. It is intended thatthe following claims be interpreted to embrace all such modificationsand changes.

What is claimed is:
 1. An apparatus for selectively activating adownhole tool in a wellbore by using a shockwave generated by adetonator assembly, comprising: an outer housing having a bore; an innerhousing disposed in the bore of the outer housing, the inner housingincluding: a chamber having at least one canted surface; an inletcommunicating with the chamber, the inlet positioned between the chamberand the detonator assembly, an outlet communicating with the chamber,the outlet positioned between the chamber and the downhole tool; and anenergy blocker disposed in the chamber, the energy blocker being freelymovable in the chamber as the inner housing changes orientation relativeto a vertical datum, the energy blocker axially aligning with the inletand the outlet when the inner housing is angularly offset less than aspecified amount relative to the vertical datum.
 2. The apparatus ofclaim 1, wherein the energy blocker is a spherical body.
 3. Theapparatus of claim 1, wherein the outer housing and the inner housingare cylindrical and the at least one surface has a conical shape.
 4. Theapparatus of claim 1, wherein the at least one canted surface is cantedtoward one of: (i) the inlet, and (ii) the outlet.
 5. The apparatus ofclaim 1, wherein the chamber includes opposing surfaces that aresubstantially transverse to the vertical datum, wherein the at least onecanted surface is formed on one of the opposing surfaces.
 6. Theapparatus of claim 1, wherein the chamber includes canted opposingsurfaces that are substantially transverse to the vertical datum.
 7. Theapparatus of claim 1, wherein the energy blocker is formed of at leastone of: (i) steel, (ii) metal, (iii) ceramic, (iv) plastic, and (iv) acomposite.
 8. An apparatus for use in a wellbore, comprising: adetonator assembly having a firing head and an initiator, the detonatorassembly being configured to generate a shock wave when activated;detonator output interrupter connectable with the detonator assembly,the detonator output interrupter having: an outer housing having a bore;an inner housing disposed in the bore of the outer housing, the innerhousing including: a chamber having a first and a second opposingsurface, each opposing surface being substantially transverse to avertical datum, wherein at least one of the first and the secondopposing surfaces is canted; an inlet communicating with the chamber,the inlet positioned between the chamber and the detonator assembly andhaving an end terminating at the first opposing surface, an outletcommunicating with the chamber and having an end terminating at thesecond opposing face, and an energy blocker disposed in the chamber, theenergy blocker being freely movable in the chamber as the inner housingchanges orientation relative to a vertical datum, the energy blockerblocking the generated shock wave by axially aligning with the inlet andthe outlet when the inner housing is angularly offset less than aspecified amount relative to the vertical datum; and a downhole toolconnectable with the detonator output interrupter, the downhole toolbeing activated by a generated shock wave that is not blocked by theenergy blocker.
 9. The apparatus of claim 8, wherein: the energy blockeris a spherical body, the outer housing and the inner housing arecylindrical, and a conical shape defines at least one of the (i) firstopposing surface, and (ii) the second opposing.
 10. The apparatus ofclaim 8, wherein at least one of: (i) the first opposing surface iscanted to the inlet, and (ii) the second opposing surface is cantedtoward the outlet.
 11. The apparatus of claim 8, wherein the firstopposing surface is canted to the inlet and the second opposing surfaceis canted toward the outlet.
 12. The apparatus of claim 8, wherein theenergy blocker is formed of at least one of: (i) steel, (ii) metal,(iii) ceramic, (iv) plastic, and (iv) a composite.
 13. The apparatus ofclaim 8, wherein the downhole tool includes a bi-directional boostercharge and a detonating cord.